//011.网格中的最大乘积
//        在下面这个 20×20 的网格中，对角线上相邻的四个元素已经用红色标记出来了，这四个数
//        的乘积为 26 × 63 × 78 × 14 = 1788696：
//
//        求在这个网格中，同一方向(上、下、左、右以及对角线)相邻四个元素最大乘积。

public class Week011 {
    private static int[][] SQUARE =
            {{8, 2, 22, 97, 38, 15, 0, 40, 0, 75, 4, 5, 7, 78, 52, 12, 50, 77, 91, 8},
                    {49, 49, 99, 40, 17, 81, 18, 57, 60, 87, 17, 40, 98, 43, 69, 48, 4, 56, 62, 0},
                    {81, 49, 31, 73, 55, 79, 14, 29, 93, 71, 40, 67, 53, 88, 30, 3, 49, 13, 36, 65},
                    {52, 70, 95, 23, 4, 60, 11, 42, 69, 24, 68, 56, 1, 32, 56, 71, 37, 2, 36, 91},
                    {22, 31, 16, 71, 51, 67, 63, 89, 41, 92, 36, 54, 22, 40, 40, 28, 66, 33, 13, 80},
                    {24, 47, 32, 60, 99, 3, 45, 2, 44, 75, 33, 53, 78, 36, 84, 20, 35, 17, 12, 50},
                    {32, 98, 81, 28, 64, 23, 67, 10, 26, 38, 40, 67, 59, 54, 70, 66, 18, 38, 64, 70},
                    {67, 26, 20, 68, 2, 62, 12, 20, 95, 63, 94, 39, 63, 8, 40, 91, 66, 49, 94, 21},
                    {24, 55, 58, 5, 66, 73, 99, 26, 97, 17, 78, 78, 96, 83, 14, 88, 34, 89, 63, 72},
                    {21, 36, 23, 9, 75, 0, 76, 44, 20, 45, 35, 14, 0, 61, 33, 97, 34, 31, 33, 95},
                    {78, 17, 53, 28, 22, 75, 31, 67, 15, 94, 3, 80, 4, 62, 16, 14, 9, 53, 56, 92},
                    {16, 39, 5, 42, 96, 35, 31, 47, 55, 58, 88, 24, 0, 17, 54, 24, 36, 29, 85, 57},
                    {86, 56, 0, 48, 35, 71, 89, 7, 5, 44, 44, 37, 44, 60, 21, 58, 51, 54, 17, 58},
                    {19, 80, 81, 68, 5, 94, 47, 69, 28, 73, 92, 13, 86, 52, 17, 77, 4, 89, 55, 40},
                    {4, 52, 8, 83, 97, 35, 99, 16, 7, 97, 57, 32, 16, 26, 26, 79, 33, 27, 98, 66},
                    {88, 36, 68, 87, 57, 62, 20, 72, 3, 46, 33, 67, 46, 55, 12, 32, 63, 93, 53, 69},
                    {4, 42, 16, 73, 38, 25, 39, 11, 24, 94, 72, 18, 8, 46, 29, 32, 40, 62, 76, 36},
                    {20, 69, 36, 41, 72, 30, 23, 88, 34, 62, 99, 69, 82, 67, 59, 85, 74, 4, 36, 16},
                    {20, 73, 35, 29, 78, 31, 90, 1, 74, 31, 49, 71, 48, 86, 81, 16, 23, 57, 5, 54},
                    {1, 70, 54, 71, 83, 51, 54, 69, 16, 92, 33, 48, 61, 43, 52, 1, 89, 19, 67, 48}};

    public static void run() {
        long ans = 0;
        int rows = SQUARE.length;
        int col = SQUARE[0].length;
        int n = 4;
        for (int i = 0; i < rows; ++i) {
            for (int j = 0; j < col; ++j) {
                long cur = 1;
                int cnt = 0;
                boolean bottom = i + n - 1 < rows;
                boolean right = j + n - 1 < col;
                if (bottom) {
                    while (cnt < n) cur *= SQUARE[i + cnt++][j];
                    if (cur > ans) ans = cur;
                    cur = 1;
                    cnt = 0;
                }
                if (right) {
                    while (cnt < n) cur *= SQUARE[i][j + cnt++];
                    if (cur > ans) ans = cur;
                    cur = 1;
                    cnt = 0;
                }
                if (bottom && right) {
                    while (cnt < n) {
                        cur *= SQUARE[i + cnt][j + cnt];
                        ++cnt;
                    }
                    if (cur > ans) ans = cur;
                    cur = 1;
                    cnt = 0;
                }
                if (bottom && j + 1 >= n) {
                    while (cnt < n) {
                        cur *= SQUARE[i + cnt][j - cnt];
                        ++cnt;
                    }
                    if (cur > ans) ans = cur;
                }
            }
        }
        System.out.println(ans);//70600674
    }

    public static void main(String[] args) {
        long startTime = System.nanoTime();
        run();
        System.out.println("\n程序运行时间：" + (System.nanoTime() - startTime) + "ns.");
    }
}
